The present invention relates to a method for producing a pipe, a carrier element being coated by means of a thermal spraying method and the material of the pipe formed later being selected as the coating material, and the coating forming the pipe subsequently being detached from the carrier element.
To produce seamless pipes, a block or a billet made of cylindrical steel is typically formed into a hollow, a short and thick-walled pipe. This hollow is then processed further in a following method step, for example, by the reciprocating rolling method or by skew rolling, to form a pipe of thinner diameter.
In more recent time, seamless pipes have also been produced by means of various thermal spraying methods. In this case, a coating material provided in powdered form is introduced into a heated processing gas jet. The powder particles melt or fuse. The processing gas is sprayed onto a carrier element by means of a spraying nozzle, so that a layer forms on the carrier element. The layer must meet two requirements. On the one hand, the layer must adhere to the carrier element during the method. Only in this way can a pipe having fixed specifications be produced. On the other hand, it is necessary for the coating material or, later, the finished pipe to be able to be detached as easily as possible from the carrier element, in order to avoid subsequent damage to the pipe.
A corresponding method is described, for example, in WO 2009/109016. In this case, seamless pipes are produced by means of a cold spraying method and the finished pipe is subsequently detached from the carrier element, in that the pipe and/or the carrier element are cooled or heated or alternatively the carrier element is melted, vaporized, or pulverized.
Depending on the layer thickness and the material of the coating material and of the carrier element, a high level or a low level of adhesion occurs between coating material and carrier element. A high level of adhesion has the result that the coating material adheres well on the carrier element during the spraying procedure, but is only to be detached from the carrier element with difficulty after being finished. This can result in an increased time and cost expenditure as a result of further method steps. In turn, a low level of adhesion has the result that the coating material adheres minimally or not at all to the carrier element during the spraying procedure, but is very easy to detach from the carrier element after manufacturing. This can again cause complications during the application of the layer on the carrier element.
It is therefore desirable to set the adhesion between coating material and carrier element so that the required adhesive properties and also layer properties can be guaranteed and production costs can simultaneously be minimized.